Automatic self-protecting hypodermic needle assembly

Abstract

An automatic self-protecting hypodermic needle assembly comprising a hypodermic syringe having a housing, a moveable plunger in the housing, a medicant chamber formed between the housing and the plunger, and a hollow needle extending from the housing in communication with the medicant chamber. A needle guard assembly is attached to the syringe housing and includes a guard housing adjacent the needle, a protective cap removably attached to the guard housing and an aperture through which the needle extends. A propellant is located in the guard housing in communication with the protective cap. When activated by an activating element, the propellant expands from a liquid to a gas, applies a pressure to the protective cap, and drives the protective cap along the length of the needle until the cap extends beyond the tip of the needle and the needle tip becomes embedded in the protective cap. Control means are provided under the operation of the medical attendant using the hypodermic syringe to automatically activate the propellant upon completion of the use of the syringe, and to embed the needle tip into the protective cap.

I claim: 
     
       1. An automatic self-protecting hypodermic needle assembly comprising: a hypodermic syringe including a housing, a moveable plunger in said housing, a medicant chamber formed between said housing and said plunger, and a hollow needle extending from said housing, said hollow needle in communication with said medicant chamber and having a tip at a distal end of said needle;   a needle guard assembly attached to said syringe housing, said needle guard assembly including:   a guard housing disposed adjacent said needle;   protective cap means removeably attached to said guard housing, said protective cap means having an aperture therethrough, said needle extending through said aperture;   said guard housing having propellant means disposed therein in communication with said protective cap means, said propellant means includes a first chemical propellant means which, when activated, expands and applies a pressure to said protective cap means;   activating means in selective communication with said propellant means to selectively activate said first chemical propellant when said activating means comes into contact with said first chemical propellant means; and   control means in communication with said activating means and actuated by depression of said plunger to activate said first chemical propellant means and produce a pressure which dislodges said protective cap means from said guard housing and moves said protective cap means along the length of said needle until said protective cap means engages the tip of said needle and said needle tip becomes embedded in said protective cap means.   
     
     
       2. The automatic self-protecting hypodermic needle assembly of claim 1 wherein said guard housing includes a propellant chamber in which said first chemical propellant means is disposed, which first chemical propellant means pressurizes said propellant chamber when activated to apply said pressure and to dislodge said protective cap means. 
     
     
       3. The automatic self-protecting hypodermic needle assembly of claim 2 wherein said control means includes a bellows disposed on said syringe housing such that a portion of said plunger actuates said bellows when said plunger is depressed into said syringe housing a predetermined amount. 
     
     
       4. The automatic self-protecting hypodermic needle assembly of claim 3 including tube means communicating between said bellows and said propellent chamber, said activating means including a second chemical activator means disposed in said tube means which when coming into contact with said first chemical propellant in said propellant chamber causes a reaction with said first chemical propellant resulting in said pressurization of said propellant chamber and dislodging of said protective cap means. 
     
     
       5. The automatic self-protecting hypodermic needle assembly of claim 4 including a dislodgable substance disposed in said tube means separating said first chemical propellant means and said second chemical activator means until said bellows is actuated by said plunger. 
     
     
       6. The automatic self-protecting hypodermic needle assembly of claim 4 wherein said one of said first chemical propellant means and said second chemical activator means is selected from the group consisting of a mixture of citric acid and sodium carbonate, a mixture of hydrogen peroxide and manganese dioxide, and a mixture of acetic acid and sodium bicarbonate. 
     
     
       7. The automatic self-protecting hypodermic needle assembly of claim 6 wherein said second chemical activator means is water. 
     
     
       8. The automatic self-protecting hypodermic needle assembly of claim 5 wherein said dislodgable substance is selected from the group consisting of petroleum jelly and wax. 
     
     
       9. The automatic self-protecting hypodermic needle assembly of claim 1 wherein said protective cap means includes flexible needle sealing means therein, said flexible needle sealing means held in a first position away from said aperture in said protective cap means by said needle when said protective cap is attached to said guard housing and when said protective cap advances along the length of said needle; said flexible needle sealing means movable to a second position sealing said aperture in said cap means against reemergence of said needle when said protective cap means advances beyond the tip of said needle.   
     
     
       10. The automatic self-protecting hypodermic needle assembly of claim 1 wherein said control means includes a rod extending from a manually operated disc adjacent said plunger, said rod having an end thereof adapted to engage a flange on said protective cap means upon actuation of said control means to dislodge said protective cap means from said guard housing causing communication between said first chemical propellant means and said activating means. 
     
     
       11. The automatic self-protecting hypodermic needle assembly of claim 1 wherein a first chamber and a second chamber are located between said guard housing and said protective cap means, said first chamber and second chamber being separated by flange means extending between said first and second chambers, said first chemical propellant means disposed in one of said first and second chambers, said activating means disposed in the other of said first and second chambers, said control means adapted to break said flange means causing communication between said first chemical propellant means and said activating means. 
     
     
       12. The automatic self-protecting hypodermic needle assembly of claim 11 wherein said flange means includes a first portion connected and extending downward from said guard housing and a second portion connected to and extending upward from said protective cap means, said first and second portions of said flange means being in mating relationship to separate said first and second chambers until said control means dislodges said protective cap means.